XAdES (XML Advanced Electronic Signature)
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XAdES applies an advanced electronic signature directly inside an XML document.
Definition
XAdES (XML Advanced Electronic Signature) is a set of extensions to the XML-DSig standard that turns a basic XML signature into an advanced electronic signature meeting regulatory requirements.
It standardises how the document itself carries the elements needed for legal validity: a reference to the signer's certificate, timestamps, a signature policy and revocation data.
How it works
XAdES defines several increasing levels of robustness:
- XAdES-B (baseline): signature plus essential attributes.
- XAdES-T: adds a timestamp proving the signing time.
- XAdES-LT / LTA: embeds certificates and revocation data for long-term validation, even after certificates expire.
The signature can be enveloped in the XML, enveloping, or detached.
Example
Spain's Facturae format requires a XAdES signature on every electronic invoice. Several continuous transaction controls (CTC) systems in Latin America — countries using a clearance model — likewise require a XAdES signature on the XML documents submitted to the tax authority.